Flashback arrester



Sept 2, 1952 E. H. SMITH FLASHBACK ARREsToR 5 sheets-sheet 1 Filed Sept.25, 1948 by E INVENTOR. ELMER f7'. SM/TH ATTORNEYS Sept 2, 1952 E. H.SMITH FLASHBACK ARRESTOR 5 Sheets-Sheet 2 Filed Sept. 25, 1948 INVENTOR.E/ MER H. S/v//TH Y @AQ ATTO/@NE vs Sept 2, 1952 E. H. SMITH FLASHBACKARRESTOR 5 Sheets-Sheet 5 Filed Sept. 25. 1948 SePt- 2, 1952 E. H. SMITHFLASHBACK ARRESTOR 5 Sheets-Sheet 4 Filed Sept. 25, 1948 INVENToR. ELMERH. SM/TH BY y ATTORNEYS Sept. 2, 1952 E. H. sMlTH FLASHBACK ARRESTOR 5Sheets-Sheet 5 Filed Sept. 25, 1948 ws .m WH. T @MA wf Patented Sept. 2,1952 FLASHBACK ARRESTER y Elmer H. Smith,'Minneapolis,';Minn., assignerto Smith WeldingEquipment Corporation, Minlhis invention relates vice vfor automatically preventing a flashbackror reverse new of ahigh'Dlssfurev gas through a pipefjjlin-ejarranged Vto 'normally conductamlow pressureeas from Ha nsource of gas supplyjtda to a new and novel'de-H point of'use lto prevent the occurrence of an eig-H- plosironfof,l`the gas. conditions Y j'Ihe 'inventionV kis Vparticularlyv WellVsuited'for use in'conn'ection with oxygen-acetylene torches;

It Vis iwell knovvn that serious and mistly explosionsjmay sometimesoccur when' wopera-ting supply means under such oxygen-acetylenetorches; shouldV vthe iblflrrririg,V gasesj'at' the tip of the torchVback-fire and causej a reverse flow of highpressure' gasthroug-h thetorch, and "gas supply pipa' particularly "if 'such high -pressure gas'should` rea-ch'Y the gas' s-upply tankfor generator. j

Tofaffrd a clearer'un'derstanding of the'V present invention;particularlyV a-s applied vto 'the handlingV of oxygen'facetylene fuelgases, such as are employed in cutting and welding torchesfit may belwell to briey dene theY actions of certai eases such as acetylene,Ywhen an explosion occurs during the operationfof'anoxygeng-acetylenejto'fch, and'vvhy js'uch explosions may occur atftheusual gassup'ply tank or generator, even though'such apparatus rnay bestationed a con# sidei'a-ble distance from' the place Where thetorchjAS' illustrativa ifapipeline isutilized for conducting'ipurejacetylenegas; under low 'pres-jY sure, usually tenjpoundsftov av torch locatedsome distanceirom the gas supply tank or generator, and' a lbackfireshould occur at the'torch tip, the acetylene inthe torchpassages'maybecome ignited' and cause a flashback vof high pressure gasthrough the'torchin the reverse direction. Such arilashback through thetorch may start a high pressure wave-traveling backy through the gassupply pipe, which may cause disassociation of the purefacetylenef eventhough the pres-sure of the gas initially was only ten pounds, which isY usually considered safe. As the hi-gh pressure Wave progresses throughthe gas sup-ply pipe in the reverse direction to its normal flow, thehigh pressure ofthe gas is maintained by ythe heat of disassociation,and the wave may continue with extreme rapid-ity,-unless interrupted inits passage through the pipeline, until it reaches the gas supply tankor generator where it may ignite theg'as and cause a serious anddamaging explosion.` y A In order. toeliminatethedan'gerwhich may 365Inayffyerce thelfWter vfrein,thetv ater seal'ba neapolis, Minn.,;afcorporation ofhlylinnesota Y i lApplication septemlm'rl 25,1921s,sleriavl,No.51243`r Y relai'm.; '(o1.4l19 2)"" result fromV suchconditions, I, have devisedanz: improvedV device, termed aa'slbackarresteri. which", `when s-ubjected'to Va predetermined high-l:v pressra' instantly interrupts the reverse' 'ow of 5'?? gasthroughthesupply line at a point aheadof th'e'nxplosive Wave,` whereby Vthereverse' flo'v'v"of explosive gas -isy effectively interrupted,Vv and`alli' danger of ani explosion occurring at the gas Sup y" source ispositively eliminated. f Flashback arresters have". heretofore Vbeen developed for preventing the' occurrence ofjex plosions in the =handlingoi"`v joxygei'1*-ac`e`t5`dene tochesmand equipment, V151313" thesetras/"el 11isllllly w been 'ofthe Wate;sealv .typeQWhere'iIl13lie"-g`el,"sl'iist"f l'S-'pass through YWater in'lits passage to thetorch* tip. Flashback arresters ofA this generaltypera-l quireafconstant'supply of water to"-assur they are always fin condition toeiectively' rup-t or block areverse dow of -high pressureflashhackarresters may eiectivelyprevnt t nj reverse now of higl 1`-pressuregasthogu he* pipe line tothe sourcev of gassupply, causabackfire at the torch tip. f l" glu Water 'type 'iiasghbak arrestarethe sp. abo egtheg Water is subject t-,olthe`v violentpres-f# through adefective; en'eck valve and render the flashback arrester inoperativ arealso known instanceswhere the water 1n waterseai has beenV drawn olfinto the line Y' gradual' 'evaporation 'er the watervf'iats Y'the' fgasfFlashback arresters of the wat r Seal "typ' therefoirejh-ave 'notteenenufely "atifsf'ctw, anna .is nfgruyg @estable tintin-esitatepoyiud'f for"`positivly prevehtigor blocking-fthe reverse?now-ofinighfpressuregasesfesultingfrornv-abacl;

45" fireat the` torch Ltip,"from reaching the-sourceVJ of zgasrlsupply.by reverse iioiyfthrough 'the-gas supplyp-ipe, which maycausfe Vseriousexplosions; "l

as-is lwelliknown.'jl. An :important Vobject-.lof thepresent 'inventioni50 therefore fisfitol provide "a" device adapted.to`l Ibei' interposedina-conduit utilized*forl'condctng an explosive 'gas' fromafsupplysource tesa".pointl-v of use, which deviceisadapted topos-itivelype-i.venta `backflow of high; pressuregas through the? 55 conduit causedfrom: an explosiona haknreror-f;

the gas at the discharge end of the conduit, and whereby the backflow ofexplosive gases cannot reach the source of gas supply and cause an eX-plosion thereof.

A further object is to provide a flashback arrester adapt-ed for use inconjunction with a conduit for conducting a combustible gas from asource oigasz'supply toa torch tip, adapted -to automaticallyinterrupt'the flow cigas throughthe conduit in the event of a suddenabnormal increase in the pressure of the gas, from any i cause, andparticularly in the event ofL a baci:- i'low of high pressure gasthrough the conduit caused by a backre or explosion ofthe fuel gas. atthe tip of the torch. i

A more specific object of the invention is to provide a ashback arresteradaptedtobtinterg-r posed in a conduit for supplying a combustible gasto a torch which device comprises a springactuated valve having triggermeans for normally retainingl it inopen positionr` to permit free gas11cm-.through the valve', andi a trigger release. being' embodiedginsaiddeviceincluding a pres,- sure.responsive element adapted" to beactuatedbyva. sudden increasevin the pressure-of the gas owingfthrough thedeviceto thereby actuate, the. trigger, and effect the release of thevalve, wh .rebyik the kSpring-actuated valve instantly moved intoclosing position to thereby positively interrupt further flow of gasthrough the device andgas supply. -conduit,

A1 further` object isVv to provide a flashback` arrester; particularlyadapted for use; in combina?. tienwith an .oxygen-.eeetylene torch forcrevette 1 ieeafloeoleow of high nreeeoreses suoli eeeeetf viene throughthe eeetvleneeiipplv conduit to tbeeoeroeo.f-;S111 io.1y,nwhieh-mevfeeoee ef Seriousexplosionief. the; eee. ettiie .source:oiieiioplyi Seid. decffmprng'- afsplngfmflg .VlVe -Whhoetineiireisfreteioed in. onen eesitionto permit free, ees-,flewtherethrough. enti e; diephiesm beiiigleiiibosied in. Seid .deveeeiiehaving one tide. operati-reir ooiiiieoted to eiiieeer i017 ifeteiiiirieVthe valve in open position, andtheoppositehside it-.the diaohiaembeieeexpoeedltoethefiow of eestiireeeii. .thedevioefwiierebywhee .efieeiiioeeiiY t--tiietoieiiitip eiidoeuees e Sudden cette .15h2325.511?? .gtl the; lll. gasllpplff cgii-szdphliim .i'futio mQVQh?.ttisserioiit eifioekiee engagement. with theveive.. niieeeiiion .the.Veive ieeiitometieelii?,movedioto.. .jteii to.` prevent. .iertiierliiow tif-.hiceA oiessuifel-seef-tiiroileii. the conduit in, the..direction,

t. lees 5.,..pe1v1souieertheeoiieuit ieedioe iremtii....d 'Dhreemtoiiievelrebeine efeuiiieieet. leest o. allow-1 the-ileso. arrester tooperate. to; close; the fvelve -beiere the highpressure ses oreli-plooien een. reach. the ve1veeiterhevins actueated the diaphragm tooperate; theitrigger; and,v T1eae-1the Vaker'.

Qtlierf objects. of the invention reside .in the simplegand.inexpensiveconstruction` of the cle.-Y vicelthe body-ef which .ispreferably made.of two Dartslto facilitate construction and assembly; in the speciclconstruction of the trigger means for retaining the,- valvein openposition during nor-.. mai-operation. ofthe torch; in the. provision ofa simple operating lever to facilitateresetting thastrigger means eachtimeit hasbeenreleased tomermit the. valve .to close.; in the -provision.of a-gsafety devicel comprising an electrically oper.-v ai.ed:.valve44which normally is retainedV in open*V position by.- a spring',- andhaving. an electric cone, trol: circuiti comprising spacedycontacts-which normally-.are in; open position .and are., adapted;

to be moved into electrical engagement with one another to close thecircuit, in the event of a sudden increase in the pressure of the gasilowing through the device, whereupon the valve is instantly moved intoclosing position to interrupt gas now through the conduit; in theprovision of a safety device of the class described comprising a bodyhaving a valve chamber-therein which is incommunication Withthegassupplyconduit, and a valve being mounted in said chamber and havingmeans for normally retaining it in open position,v and a pressureresponsive element also being located in said body and having anoperative connection with the valve retaining means, said-.valvechamberhaving one end 0f an elongatedvcondutI in communication therewithfor conducting the fuel gas from the valve chamber (to said element,said conduit being of sufficient .length-.to allow the valve ample timeto close before a backflow of high pressure gas can reach thvaflveChamber 11.1 $1.1? @Vent Cf'fn, QXPflQQn et .the torch tip eeueineeSudden beeisiiov et. high.: pressure gasthrough said bodyyand in:lthenpr-r vision. of e eefets7 devieewhieh readily lendeit' for use inconjunction with the'..fuel.gas s upp matically interrupting. the.` ow.of A gas y. throng, said conduit, in the event of a sudden,increas;l inlthe pressure of thegas flowing tllerethrougj-h,V regardless ofthe.oeueee oi Stich) "pressure,

These. erid other. objects-oi Athe...inv-enti@.1.1...e.r.1.ti.V themeansfor. their 'att inxnentAV will be. :no apparentirom thefoilowingideserieton eonneetioo with. thev accompanying drawings In theeeeompenving drewmes .there eene disclosed a structure designed tocarry4out t., various objects of the invention, -hutit' sp1-,onlinrvunderstood that the inventionit Doteonioetto the exact features showrnaslvarigus change: i JmayK1 oemede Within the eoopeoitiie. elei whichfollows.

1.1i' vthe drawingerA Figure 1 ie e diagrammatic view elioving. the..iieshbeekerreeteif intereoririeetediii theaeet iene.. 'supply conduit eianoXYsen-eeetyielie to .Figure 2;.iee eide View of enineteiletiori lertothe one. shown in Eieure..1,.o.n. enenlareeii.; Seeles Showingthe.eeietv device .adapted ion/Leit. mounting.:

Figure' 3 is a vertical sectional View on thvge, l i r,ieN 3:-3of`Figure 2, on'an enlargedscaleshowing the. valvein open position.andthewtrigger actuatf. ing'diaphragrn in its normal posii ,Y

Figure. .else view'similet to. Fieiiifo, betogers-- the valve in.eioeedieeeition, ets- When released.. by thetrigger means. asa resultofthe;triggen`v diaphragm haring beeiifeetuetedlbyfen. ebrio, melliahishfeieeeore. in the: fueljeesfeiioplyte nefdum F'euref 51, iSf.-.eflSeoftioiiel vieil. `View on, the-linee.- ivi-efziiieore.;

e-,ii is e; bottoni .View ofthe-Hackmeeting Eisele-'1 is-.e..:.vi.ewShowing@ iieetiheoieetreeterfoieiieiitlrmooiiied: eoiietiuetiea th.veivebeie .a showniliitsfrio.V operi positie Figoi'efe is e..v..W,-Sirr.i.i.1e.r Fictie-.7j but.; Showing. the velveelosedvese resi-1notitie-.dias enfasis-.secured theietehaving been. dieter-.tecleaa-.sudden increase in they pressure of the, gas -loyvfNv ing-throughtheconduit; l

Fgure- 9; isa View; showing a flashbacklarresten.:

comprising a, solenoid-operated valve, thefvalveg ybeing shownin,normalgopenfposition; endet Figure v .is a.view;z similar to `lEg-ure9, but4 showing the .valve clo'sed as aresult of thepsole-A noid.fcontrol circuit having been .closed byrasud.-`

denrincrease the pressure. through the conduit.. v

-In the selected embodiment of the herein disclosed, there isdiagrammatically illus- 5 tratedin Figure 1, a .conventional acetylenegeneratorpgenerally. designated by ther.,numera1 q2 andhaving al conduit3y `leading therefrom andV of the gas..flot/irisl j connected to theintake 4 of a conventional presl sure-A regulator 5, having a -pressureindicating gau'geli for indicating the pressure of the acet,.

ylene or fuel gas owing through the. conduit 3.v

The novel safety device herein disclosed is adapted tobe .interconnectedVin the conduit g3. between the generator 2 or-.othengas supply.Vsource, and .the .usual oxygen-acetylene..torch, .a

generally-designated by the'numeral'l. f.. The constructionV of .thesafety device or flash-1 backarrester is best illustrated: in Figures 3andl 4, and'comprises a body, generally designated by:

the numeral 8, comprising upper. and lower parts' 9 .and-LI I,respectively, -boltedtogether by suitablebolts or screws. i2, asshown-in Figure .2;

The. lower partllis provided with` a1 seat I3.

shown surrounded by an upright flange 14.. rEhe lowerpart. II .is shownlprovided with a; second..V seatal fof slightlysmaller diameter than theseat I3,:adapted to receivea` diaphragm I6, asclearly illustrated inFigures 3 and 4. The diaphragm.:

I6 isfslightly thicker than the depth of the seat lz-whereby when thelower end of the upper part 1 9 is placed upon the seat I3 and issecured theretoxby the bolts I2, the marginal edge `of the diaphragm I6will be compressed between the parts 9 and II to thereby provide a.leak-tight jointv between said parts.

A fvalve chamber I'I is provided in theupperV part Shaving a valve seatI8l at'its bottom adapt. edto be engaged by a valve I9. vA spring 2l hasits lower. end engaged with the 'valve I9 and its f upper end is.seatedf against the bottom 22 of a counterbore provided in a-nut` 23,receivedA in threaded engagement with the upper end of the part 9, vasclearlyillustrated in theY drawings.

The spring serves to constantlyexert a downward pressure against thevalve I9 to move it into closing Yengagement with its seat i8.V Thevalve. chamber Il has -an outlet 2d which is of: aconduit `26 connectedthereto, as will be understood by reference to Figures 1 andl 2. y

rIhe .upper part 9 of the bodyof theV device isv shown having an intake21 located directly below ther-valve i9.V Theintakeis threaded. toreceive..

onel end of apconduit 28, including ttings 29 and...

3| and a union 32. The opposite end of the con duit 28 is connected tothe discharge side-.33 of the pressure regulator 5. An auxiliary chamberthreadedtov receive a tting..25 having one'v end 34 beneath the valveseat I8 is in constant com' munication with the pressure regulator?).throughI the conduit 28, as will rbe understood by. refer. ence toFigures 1 and 3,. .Y

.The bottom of. the chamber 34 `is shown provided with an upstandingboss 35 having a bore therein for guidingly receiving a hollow valvestern 3-6 of the valve lil. A small plate 31 is preferably secured tothebottom` of the Valve stein 35fandA is seated against theupper Aface ofthe diaphragmfl by the compression spring ZI er1- gaged with the valveI9. The spring 2l thusl constantly tends to urge the valve and diayphragm into valve closing position, asA shown in Figure 4Q nivSuitablevents 38 establish .communicationbetweeii the chamber 34 and thespace39:

provided above the diaphragm I6, thereby to preventfthe `formation of avacuum yin the chamber" 34 or lspace l39, ywhen* the diaphragmisactuatedf=r The lower. vpartII ofthe body of the device is shown,.provided -at its bottom` end4 with vascllqiarm?` ber;i, .-normal1yclosedbv a .0.211142 having Suitable means .such as boltsor screwsy il),for; detachably securing-Vitto' the part Il. Thechamber 6I houses atrigger mechanism which serves f to normally'retain the valve I9 in openposition.

The trigger mechanism comprises a trigger. 43A f, supported on asuitable pivot '4 anchored in the wall of the chamber 4l. The triggerhas a laterally` extending detent d5 adapted to engage a notchgorshoulder 45 provided on a hollow stem ll?, slidably supported in a'guidebore provided in the part vil directly belowthediaphragm Iii,V as willbev .understood by reference .to-Figures 3W. and 4, A circular plate ordisk 48 is securedto -g the upper endfpoi the sternv il and bearsagainst the bottom face of the diaphragm I6,

A small yoke @9, best shown inFigure 5 stradey dlesgthe lower end ofYthe stem ifi and hasonef. r endV oiA a-vpin 5I received in a recessprovided ing` The opppsiteendf;

the ,closed` end of the yoke. of the pin is engaged with a head52;having. a

threaded portion 53 received inra-n aperture pro-fw. vided in adiaphragm 54. A nut 55 secures the head 52 to the diaphragm for directmovementl therewith. The diaphragm is supportedinthe..

bottom of athreaded socketprovided in the lower part I i, and is shownsecured in positionthere-v; in by a nut 55, a suitable gasket 51 beingpro-V `videdmbetween the marginal edge of. .the diaphragmd and the innerend oi the nut 56 to provide a sealtight connection between the nut andpart II.

The -nut 5S is shown having a threaded aper;1. .ture adapted to receiveone end of. a fittingnBS, having an intake 59, to which the other end{of the conduit 26 is connected,Y as bestA shown in Figure l. Anoutletis provided in the fitting. s 58 to which one end .of a fuel supplyconduit 62 is connected. The opposite end of conduit 62 connected, asillustrated in Figure l.. It willv thus be noted by reference to Figure4,; that the diaphragm 54 is always' exposed to the pressure of y theuid flowing through thetting 58, regard.l 4less of the directional flowof the gases there 1 through.

The terminalslof the spaced. legs of the yoke 481 are shown notched toreceive Vthe. end portions of a pin 63, received in a'transverseaperture'pror'; vided at the `upper'end of the trigger 43, whereU Vvlbythe. detent 45 of the trigger is alwaysretained inoperative relationte the notch dlin-the stein-l 41, as.-;will besunderstood .byreferenceto liguresl 49, and also whereby the opposite end of-theyoke isheld in contact with the pin 5i as will beunderstood. Vents EVS are.provided in the` lower Dart vrll to establish communication:betweenthe1 Y chamber 4l .and the. spaceprovided'beneath the l' aca-tegamesaprete-masi, tterbyltoiperait permettaient@ ofthe :diaphragmwithbutre'straint; l

Means isV 'providedA vfr' ymanually resetting the inerease'inthepressure ofthe gasv ilowingthrough theet'tin'g 58. Such means is shown'comprising a pushrd B9 provided" at its lupper `end with a' reducedterminal-lVreceivedin a bore provided mtheflowerendlof the stern4l andwhereby the forkedand has a pin'l2 connecting-itto a -v'alve' sire'cl,be`-made-inltwo -partsjas `it does not require" tliatitr-befretainedinengagement with the lower part l ibya sealtig-htjoint.` The lever 13 isnor; mallylpositiorledas indicated in dotted lines" in' Figure 3,and-when swung tol the full lineposi-v tiofshownin tliisg'ure', the pushrod 68 is moved upwardly to '-thereby'impart a similar movementto-theste'rn'- "dhfceritral .porti'onof the diaphragm! isdmov'edintoopen-position'. When' the arbve partsare'lthu's operated, the notchorshoulder? normal operating conditions, the fuel gas vwillvfimfandwconduit 2li-fitting 58, and thence into the co'n'dui-t` (i2-whichconducts' the-gas -to `the'torchv 'lyasindicated in Figure l.

Anf important `feature-1in the construction ofthe Aashback arresterherein disclosed resides thelength of the conduit 26, which'must-besuchthatfinitheevent'of a sudden' reverse flow of high pressuregas'in the conduit 62, vcaused possibly by? an explosion or backfire ofthe fuel gas at the' tip of 'the f'torch," the valve I 9,' .whenreleased, will hveiample'time'to'move into closingposition bei'foren-theY high pressure 'gas lreaches rthe valve chamber yl'l. I

the-event of a backfire or explosion' ofwthe fuelgas Vin the torch;causing albackflow ofv a'- high-pressuregas-through the conduit 62',such backow of high pressure gas will distort the-dia` phragm` 54; asshown inv Figure 4, and causeit to= move; the trigger 43 out Vof lockingengagement;v

with? the' shoulder 46 ofthe-'stem' 4l, whereupon the-valve i9- isinstantly moved into .closing er1-f gagement'withthe valve seatl I8 bythe action ofV thee-spring v2l,vtofthereby-shut' off anypossible 28 -of-the -valve- `chamber Il.

stated,` the conduit 2B is made amply long to'positively prevent anybackilow gases entering there; in-vfromreaching the valve chamber l1,after the valyehas closed:

The-.trigger operating diaphragm 54 is constantly exposed to 'the flowof gases through-the Y conduit 26,and` the tension-of ethe-spring-Missol I adustedthat the spring-willhold thediaphra'g'm;

s againsi'iVv distortion? under"AL all normal operating pressures; Byso'adjustin'githespring*64; harmi' lessfpressue' rise'sin th line whichmay be caused@v by* nzrmal`r 'pressure'variations at- 'the gas 'sourceV`and will not actuate the diaphragmto causeitto V actat'e'the triggerand thus unnecessarily release theshtoivalve I9.'

It willi thus be 'seen that a back-fire or baclnlowH of'highf pressuregases through the fuelsupply: conduit "62" cannot reach thegeneratori-'orx'gasl" supplysource'and oaus'e'an explosion at the'generatbr or other-gas supply source, with itsv resultant damages' tovequipment'and'possible bodily."

injuryto' 'attendants.v v

Figures? 'and 8 illustrate a a'shback arrester of Vsomewhatrdilerentconstruction, comprising a'A springlactuatedvalve 16 vmounted forsliding.y movement in -a -bore 11 providedvn the upper part of avalvebo'dy.' generally designated by# the numeral 18.? The conduit' 19leads from the usual discharge' 33 of the pressure regulator 6 andconducts lower pressure fuel gas into the-bore 1l of the safety. device18. A conduit 8l, corresponding 'to the Vconduit26`of the previousgures,

condiicts the low` pressure fuel gas from the'A bore Tl into achamber 82located beneath a-di aphragm 83 'provided in the lower part 84 of theeompositebody 18 of the ashback arrester. Ar secondvconduit '85,corresponding to the conduit 62 in Figure 1, leads from the device 'IBYto the`l` torch 1,' as'will be understood. The lowerpart 84 ofthedevice' is shown'hav-i ing a threaded extension 8'! at its upper end'adapted to bef received in threaded engagement with the lower-end of theupper part 80; Theext'ension 81 isinternally threaded toadjustablyreceive an abutment member 88 for one end of a spring 89.shown coiled about the Valve-16. l' The lower end of the spring isseatedagainst a plate 19 I' between which' and a second plate or disk 92;

the central `portion of the diaphragm 83 is clamped-by a suitable nut93. The bottom of the part v84 is made concave as shown in Figure 7,.and cooperates 'with the diaphragm 83 to provide a chamber V94 adaptedto receive the diaphragm inthe event of a sudden excessive pressure defveloping in the conduitvl, and adds asa stopl to prevent rupture ofdiaphragm.

In the operation of the safety device shownfinl Figures '7 and 8, lowpressure -fuel gas is delivered f into the bore 'l1 from the conduit'18,.it beingunderstood that the -valve I6 is retained in operi#position byfthe' action of the spring 89. From the bore 'H the lowpressure gas ows through the conduit 8 l' whichya's in Figure 1, is ofsumcient length to permit the valv'to'close in the-'eventi' ofa'suddenincrease inpressure in' the gas flow-P ing through the conduit 8I.

Under normal operating conditions the i ga's ows through the open valveandthence into' the I chamber 82 beneath the diaphragm-83, and fromthere-into the conduit -to the torch or point of? use "of the gas'.l The-tensionin the spring-89 ,such that under normal operating conditions,the'l valve lis. maintained in openposition to permit reesow of lowpressure gs through thesafety device. l

Shouldan explosion or backfire occur'at the tip of the torch causing-Ya-suddenf` back'loivle!U high pressure gas throughl the -pipe 85 and'into the chamber' 82, such high -pressure gas will 'dis-'' tort thediaphragm83 and move it into the position shown in Figure 8, whereby thevalve'll isA closed to positively cut olf any possible gas'ow 1throughthe valve# bore 111 tothe conduit `"19;

. In Figures 9 and 10 there v9 The valve will remain closed so. longasthe high pressure exists -in the conduits Vand, 85. As soon as thepressure drops to a predetermined figure, ,thevalve is automaticallyopened to permit normal owr of low pressure gas through. the' safetydevice, and therefore normal resumption of the equipment.

lisillustrated an '.electrically operated safety device which,v liketheones shown in the previous figures, has .a presl' sure responsiveelement `or diaphragm, one ,side of which is constantly exposed'to thepressure of the fuel gas flowing through the device to the torch orpoint of use.

The device comprises a valve body, generally designated by the numeral95, having a lower portion 96 provided with a valve chamber 9'! in whicha cup-shaped Valve 98 is mounted for sliding movement. One end of thelower portion 96 of the valve body 95, is threadedA to receive one endof a conduit 90, corresponding to the conduit 28 of the structure vshownin Figure' l, and from which low pressure gas isl delivered into thevalve chamber 91 vfrom the gas supply conduit 3 of the generator.Thehoppositle end of the lower portion 96 of the body 95'is similarlyFigure 9.; The spring |00 normally retains the valve 98 in its openposition, asshown in Fig-i ure 9. The valve is preferably constructed ofa suitable nonferrous metal, and has its upper endsecured to a body|0|'?of a suitable ferrous metal slidable--in asleevef7|02 4securedgin'fthe V75-upperl portion Vof nthe body 95'by a suitablehicap, |04 A disk03, preferably ofinon-ferrousf metal, 'Vis' shown interposed between theupper lend of the body |0| and the cap |04.

A solenoid, generally designated by the numeral |05, comprises asuitable winding which is xedly secured in position within the body 95below the sleeve |02. The solenoid coil |05 is made cylindrical incross-section, and thus cooperates with the sleeve |02 and the wall ofthe valve chamber 9 1 to provide an elongated guide for the valve member93 in its movements into and out of closing positions.

From the body 95 the low pressure gas is conducted by the conduit 89into a chamber |595 of a second body, generally designated by thenumeral |01, composed of lower and upper parts |08 and |09,respectively. A suitable diaphragm is interposed between the parts |08and |09, and is firmly clamped therebetween by manipulation of suitablebolts or screws, not shown.

An opening ||2 establishes communication between the bore |06 and ashallow space H3 provided beneath the diaphragm i whereby the majorportion ofthe bottom surface of the diaphragm is exposed to the pressureof the fuel gas flowing through the bore |05 and into a conduit l I4which conducts the fuel gas to the torch or point of use.

The upper part |09 of the device l has its bottom face counterbored orrecessed to provide a chamber H5 adapted to provide clearance for thediaphragm when distorted, by excessive gas pressure in the bore |06.

A suitable switch, generally designated by the numeral H6 is shownprovided with a iixed contact ||1 and a .movable contact H8, lconnectedrespectively 'to electric wires ||9 and |2|l which connect the switch||6 to the solenoidcoill,|05.

The wire |19 is shown adapted to be connected toa source ,of electricenergy, not shown.v

A smalll pushgrod |22 isSlidably-mountedirr a nut |23 received inVthreaded"engagementgwith .the Walls of an' `ripening |20 providednthejupner.

part meer thevbpdy m1,.,'rne nut, 1,23A is: axially adjustable inthei091e|20to varyvthetension in a spring Iza having one1 en d seated.against .fthe .nut 123 end having its opposite-.end- .Seated Qn geniali,disk l2 5 engaged .With the diaphragm i whereby the spring constantlyexertsat down- .ward pressure against the diaphragm ,vtogvretain it inswitch-opening position, as indicated in Figure. vUnder normal,operating conditions,y th e valve `|`0| is retained in open .positionbygthe; spring solenoid |05 to. becomeenergize instantly move the valve0,8intol1ts closed engagement with the iredcontactl |00 whereby thefuelA gas VVmay flowguninterruptedly from the conduit 910 throughtheconduit.g 9, which it is to be understood is of sufiicientlength topermitl the valve. time rto, close before. the high pressure gas canlreach'A the valve chamber 91, should an explosion or backfirel occur,causinga baclriiow of the fuel gases. thr9ugh,.vthe system. In thelevent offsuch a backiiow; of fhigh pressure gas in the conduitllllvandlbor 106, the diaphragm isdistorted, as showni- Figure l0,whereby the push-rod |22-isactuated to move the movable contact I8 intocircuit closing Such closing ofthe switch |.|.6wi

`remain in switchiclosing Iposition* as sh Figure 10., i. Y

Sure in fthe Conduit: U4 'agito/re, .lgierggins above normal operating.lpressure orisrelatively greater than the pressure eXertedfonthe-1diacally interrupting or preventing any possible backflow of high pressuregases through the conduits 62 and 3 to the source of gas supply. Thedevice operates automatically to temporarily interrupt fiuid flowthrough the apparatus, whenever the pressure of the gas flowingtherethrough exceeds a predetermined pressure.

In the form shown in Figures 1 to 6, inclusive, manual manipulation ofthe lever 13 is required to reset the valve in its open position,following each interruption of gas flow through the device, causing thevalve to automatically close. The fact that the valve requires manualresetting may be considered an advantage in that it gives the operatoran opportunity to carefully inspect the apparatus following eachbackfire or explosion of the fuel gases causing a backflow of highpressure gas throughthe torch and fuel supply conduits. v

In the form shown in Figures 7 and 8, the valve 16 automatically returnsto its open position when the pressure of the gas diminishes to itsnormal operating pressure. Such automatic opening of the valve alsooccurs in the form illustrated in Figures 9 and 10, when the presy surein the valve chamber is reduced to normal.

The novel ash arrestor herein disclosed in its various forms has beenfound to positively prevent a backflow of high pressure combustible gasin a torch and its fuel gas supply conduit from reaching the source ofgas supply and igniting

